Spinocerebellar ataxia type 2: clinical features of a pedigree displaying prominent frontal-executive dysfunction

Spinocerebellar ataxia type 2 (SCA2) is a recently delineated cause of autosomal dominant cerebellar ataxia type I. The basic clinical neurologic features of SCA2 have been described in the literature, but neuropsychological features have not, despite statements that some patients became demented.

To describe the clinical and neuropsychological features of patients from a pedigree with SCA2.

We studied 8 affected members of an Australian pedigree of northern Italian origin with autosomal dominant cerebellar ataxia type I caused by SCA2. Patients underwent clinical neurologic examination and abbreviated neuropsychological testing, while some also underwent magnetic resonance imaging. The results were compared with pooled results from previously published studies of patients with SCA2.

The pedigree displayed anticipation, with earlier onset in later generations, and there was an inverse correlation between repeat number and age at onset. The principal difference from other clinical reports of SCA2 was our finding of unequivocal frontal-executive dysfunction in 5 of 6 individuals who could be tested quantitatively, despite Mini-Mental State Examination scores in the nondemented range. This feature did not appear to correlate with either repeat size or duration of illness.

In light of a recent report of frontal-executive dysfunction in spinocerebellar ataxia type III, we postulate that this pattern may be common to the autosomal dominant cerebellar ataxias and frequently may be overlooked because of the insensitivity of routine screening tests such as the Mini-Mental State Examination.